The present invention relates to a tension controlling device for the connection of members held in tension.
Many devices today employ a tension member to connect a flexible member to a relatively fixed member. One example is found in automatic garage door operators which use a flexible member such as a belt or chain to raise and lower the garage door. The flexible member is secured to a trolley which is linearly moved by an electrical motor to raise and lower the door. A tensioning device which includes a spring to maintain substantially constant tension in the flexible member and to counter the shocks of starting and stopping the door movement is used to connect the flexible member and the trolley.
One such device is described in U.S. Pat. No. 5,297,782 to Dombrowski et al. and includes a threaded shaft connecting a flexible member through an aperture in a trolley. A snubber unit is screwed onto the threaded shaft until the tension in the flexible member is approximately correct as judged by an assembler. At this time, a split ring keeper is removed from the snubber unit, which releases a spring to push against the trolley, finally adjusting the tension.
The Dombrowski et al. arrangement has performed well, however, the final tensioning of the flexible member is the result of adjusting the tension without the added spring tension, then later adjusting the tension with the added spring tension. Further, the removal of the split ring has been found difficult, particularly by home assemblers of a garage door system. Lastly, the final tension of the flexible member, which is important to the operation of the system, is left to the eye of the assembler which may vary from case to case.
A need exists for an improved apparatus for connection and tension adjustment between a first member and a flexible member which is easy to install and which controls the tension of the connection.